Classifying curls: New system streamlines purchase decisions for underrepresented hair textures

27 Mar 2023 --- A new classification system that leverages optical microscopy to study unique hair properties may soon help consumers pick products most suitable for their hair type. To create this guide, a team of researchers led by Michelle Gaines, assistant professor at Spelman College, US, has investigated underrepresented hair textures to streamline consumers’ hair care shopping experience and achieve more consistent results.

As an African American woman, Gaines was confused about what products worked best for her reportedly under-researched hair texture. Her team measured the mechanical properties of wavy, curly and kinky hairs with a texture analyzer and a dynamic mechanical analyzer. 

According to Gaines, most prior research on hair properties was conducted on wavy or straight strands from white or Asian people. She says that less is known about what has traditionally been called “African” hair. 

“As a polymer chemist and materials scientist, I thought it would be great to start a project where I could study the nuances of my hair because I felt like it wasn’t very well understood,” she remarks. 

Specifications in a new hair category system
The research takes inspiration from other approaches to classifying hair types, such as those from hair stylist Andre Walker. Walker’s system –  a classification system also known as The Hair Chart – ranges from straight to kinky, including tight coils and zig-zag strands with angular bends. 

While the Hair Chart has long been used as a common benchmark, advancing upon this conventional system is something hair care innovators have been innovating around this year. Myavana, for instance, recently introduced an AI-supported platform that identifies a combination of textures and types that a person has to produce more precise digital hair profiles for every consumer.

Lead researcher, Michelle Gaines, created a study to eradicate product confusion for women with curly and kinky hair. Similarly, Gaines felt that traditional systems like the Hair Chart worked well for straight and wavy hair, but lacked further nuances to distinguish the many curly and kinky hair varieties. 

She wanted to see if she could identify differences in properties other than curl shape and tightness and then use those differences to develop a more precise and quantitative classification system.

Through her observations, she aims to guide a more comprehensive hair classification method than what is currently employed industry-wide to create a more inclusive approach. 

Measuring curls and counting contours 
The Spelman College team has developed the “stretch ratio,” which is a new parameter to quantify and compare the force required to uncurl a strand until it’s straight. That ratio was negligible for straight hair (since it can’t be uncurled), about 0.8 for wavy, 1.1 for kinky and 1.4 for curly. 

This measurement could be used as an indicator of the initial curliness of a sample, providing a quantifiable way to distinguish between these types.

Additionally, the team measured geometric properties, such as the diameter, cross-section and 3D shape of strands, using optical microscopy, scanning electron microscopy and a camera. 

The researchers also developed new parameters, including the number of complete waves, curls, or coils – also known as contours – that they measured on three-cm lengths of hair. 

They found that wavy hair has less than one full contour in that length, curly has about two, and kinky/coily has approximately three or more. The results suggest that people can classify their hair by counting contours.

Helping ease purchasing paralysis
Gaines used to rely on chemical relaxers to straighten her tresses but stopped when she became pregnant. 

When searching for alternative solutions to hair care, she felt confronted with an overwhelming variety of products available to style and care for natural hair. Cuticle layers that protect the hair surface are smoother, larger and further apart (left) in wavy hair than in curlier hair (right) (Image credit: Michelle Gaines).

“As an African American, I was born with very curly, seemingly unmanageable hair, and other ethnicities can possess similar hair properties,” she says. 

Gaines hopes the team’s findings will identify the best parameters for developers to design and for consumers to select the most suitable products for each hair category.

Zooming into cuticle layers
The researchers presented their findings at the American Chemical Society (ACS) spring meeting yesterday. ACS Spring 2023 is a virtual and in-person hybrid meeting from March 26 to 30. The conference features more than 10,000 presentations on a wide range of science topics.

Now, Gaines has taken the research further by examining the layer that protects the surface of each hair fiber, known as the cuticle. Cuticles naturally open and close reversibly when exposed to water, shampoo and conditioner. 

However, excessive acid and moisture retention can cause permanent damage to the cuticles, causing them to remain irreversibly lifted, thus exposing the inner cortex of the hair fiber. 

Irreversibly lifted cuticles, which effortlessly open and close, make the strand more porous, which causes more moisture absorption. 

Gaines’ preliminary findings show the cuticle layers are larger and spaced further apart in wavy hair than in curly and coily hair. Also, the cuticle edges are smoother in wavy hair. 

These findings could help the researchers explain why curly and coily locks dry out faster than wavy and straight hair. 

Natural hair care
Earlier this year, Californian biotech company Amyris launched 4U by Tia, a natural hair care line co-developed with Tia Mowry – actress, daytime talk show host and 4U brand founder. It featured Amyris’ “breakthrough” moisture-locking ingredient coined as a plant-based alternative to silicone in hair products.

Additionally, Procter & Gamble Beauty expanded its portfolio of brands by adding Mielle Organics, with the intention of making hair products and services for consumers with textured hair more accessible. The brand also went viral on TikTok after one of its hair oils was promoted by various influencers, leading to it selling out at US retail outlets.

Edited by Sabine Waldeck